Coal stoker



Jan. 21, 1936.

w. M. cRoss,-JR.. ETAL COAL STOKER Filed June 9, 1932 2 Sheets-Sheet 1 .pllllllllllIllillllllilfil,

A RNEY.

Jan. 21, 1936'. w, M. cRoss, JR., ET AL Y 2,023,274

COAL STOKER Filed June 9, 1932 2 Sheets-Sheet 2 IN VEN TORS` ATT NEY.

Patented Jan. 21, 1936 STATES PATENT OFFICE coAL s'roKEa v Walter M. Cross, Jr., Charles G. Budel', and Victor C. Norquist, Kansas City, Mc.,

assignors, 'by

direct and mesme assignments, of one-half to Mid-Continent Investment Company, Kansas City, Mo., a corporation of Missouri, half to Butler Manufacturing Company,

and one- Kansas City, Mo., a corporation of Missouri Application I.Func 9, 1932, Serial No. 616,258 3 Claims. (Cl. llt-MDI) matic 'stokers a blower is used to support theA combustion in the combustion pot in `which the coal burns from the top downwardly or in what is commonly termed an underfeed stoker. Frequntly the furnace fire tends to clinker and form slag at'the surface. vent the free passage of air out through the combustion space and the result is that back Smoking will occur.

It has been suggested, to prevent back smoking,

to place the coal duct under a slight pressure either from an independent source Aor from the air in the air duct. In practice, it has been found vthat this'will not prevent back smoking due to the fact that a cyclic circulation is set up within the coal duct by the positive pressura.

causing the smoke and coal dust to issue from .the coal hopper. This is particularly true when the fire' has become slagged or when it has dropped to near the level of the coal duct. rll'hen, too, if the supply of fuel becomes low, the pressure will escape through the coal hopper and back smoking will occur readily.

One object of our invention vis to provide a means for stopping back smoking by sucking the smoke from the coal duct before it reaches the coal hopper and thus preventing its escape under all conditions.

Further objects` of our invention will appear from the following description.

In the accompanying drawings which form part of the instant specification and which are to 'be read in conjunction therewith and inwhichv like reference numerals are used to indicate like parts in the various views;

' 2-2 of Figure l.

'l Figure `3.

Figure 1 represents a plan view of one embodiment of our invention.

Figure 2 is a lsectional view taken on the line Figure 3 is a fragmentary sectional view of a modification embodying our inventioni Figure 4 is a sectional view of a modification .f of the form of our invention shown in Figure 3.

Figure 5 is a sectionaly view of another modification ofthe form of our invention shown in This slag cap tends to pre-` In general our invention contemplates creating a partial vacuum or suction in the coal dustr by means of the air in the air duct and utilizing this suction to carry away the products of combustion which escape into the coal duct and which, 5

if permitted to escape from the coaly hopper, will cause back smoking. In its broadest scope our invention consists in causing a reduced pressure in the coal duct.

More particularly referring now to the drawings, Figure 1 lshows a plan view of a conventional automatic .underfeed coal stoker in which the motor I drives the fan which is encased in housing 2, and a transmission 3 which rotates the coal screw t which is situated in coal hopper 5. The coal duct 6 connects the coal hopper 5 and the combustion pot l. An air duct f. 8 is provided either coaxial with the coal duct 6 or parallel thereto and receives air from the air blower through air passage 9. The air is supplied 20 to the combustion pot through tuyres, as is` well understood in the art.l An injector nozzle It! is tted to the coal ductkbymeans of connection It as can readily be seen by reference to Figure 2.

The air in the air duct 8 passing through nozzle 25 I0 will create a partial vacuum in the connection II which leads to the coal duct so that any smoke present therein will be carried by the ejector out through pipe I2, 'Pipe I2 may be led back into the air duct, to a special tuyre in the 30 combustion pot, into the combustion space per se, I into the stack, into the ash pit, or out of doors.

The salient feature is that the smoke will be ,carried out of the basement in which the st oker is located and thus prevent the obnoxious features 35 of back smoking. It is obvious, of course, that the smoke of back smoking contains Vsulphur bearing gases, carbon monoxide, and other gases which are deleterious to thehealth.

In the form shown parallel Ato coal duct 6 The Venturi tube I3 is connected to the air duct 8a by branch leads I4 and I5. At the point of. maximum velocity -a.

I connecting pipe II is tted to the coal duct as before so that the gases will escape into the 45 rapidly moving air through the Venturi section and be carried by branch pipe I5 into the air duct.

- In this modification a. difference of pressure can be obtained by the design of the Venturi section and is assisted by the pressure drop in the airj50 duct due to friction.

In the form shown in Figure- 4, the varrangement is the same as that shown in Figure 3 in which a Venturi section I3 is employed. In this modication a cowling I6 is iitted over" the ex.

the bottom of the la in Figure 3 air duct 8c is 40 haust end of the duct 65a leading from the Venturi tube so that the passage of the air over the cowling will create a zone of reduced pressure in its vicinity assisting in the discharge of the smoke into the air duct 8a.

In the form shown in Figure 5 we place septum l l in the air duct 8a to provide for the reduction of pressure to assist the Venturi tube in creating a cyclic ilow through the Venturi tube I3 and branch pipe i512, thus obtaining a positive suction due to the :.lction M into the air duct 8a insuring the Withdrawal of volatiles VWhich are present in the coal duct 6 due to back smoking.

It is believed that the operation of our device will be obvious from the above description. We are enabled, by the use of a Venturi section or by an ejector to convert the potential energy of pressure into the kinetic energy of velocity and to use this energy to create a zone of reduced pressure to suck the products of back smoking out of the coal duct and discharge the same into the combustion space where they will be passed out through the stack. We are enabled to obviate the diiilculties of back smoking in a positive manner which will function irrespective of the level of the fire in the combustion pot or of the amount of coal in the coal hopper. It will be seen that this eliminates the disadvantages of the method of preventing back smoking hitherto proposed,

obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is,

Vclaim is:

aoaaave therefore, to be understood that our invention is not to be limited to the specic details shown and described.

It will be noted that we have shown a valve 22 in each of Figures 3, 4, and 5. This valve controls the air admitted to the Venturi section and it is possible by manipulation of the valve to control the suction in order to prevent it from becoming so great as to tend to draw smoke and ame into the coal duct. It is believed that the operation of this valve will be obvious from the drawings.

Having thus described our invention, what we 1. A coal stoker including in combination a coal hopper, a coal duct communicating therewith, means for conveying coal therealong, an air duct adapted to supply air for coal being burned, a fan for blowing air through said air duct, an ejector device having a suction leg, means for supplying air from said air duct to said ejector device as the ejecting medium, and means for placing the suction leg in communication with said coal duct, the construction being such that smoke and gas in said coal duct will be entrained in the Aejecting medium, and prevented from escaping from said hopper.

2. A stoker as in claim 1 including means for controlling the air supply to said ejector device.

3. An automatic coal stoker including a coal duct, an air duct, means supplying air thereto, a smaller duct communicating at both ends with said air duct and including means causing the pressure of the air from the air duct to increase the velocity of the air in the smaller duct and a duct establishing communication between said last named means and the coal duct.

Y WALTER M. CROSS. Jn. VICTOR C. NORQUIST. CHARLES G. BUDER. 

